Published online 25 January 2008
Published in Soil Sci Soc Am J 72:362-369 (2008)
DOI: 10.2136/sssaj2006.0394
© 2008 Soil Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
SOIL CHEMISTRY
Characterization of Organo-Mineral Aggregates of Chernozem in Northeast China and Their Adsorption Behavior to Phenanthrene
Qing Huanga,b,
Fasheng Lia,*,
Ru Xiaoc,
Qunhui Wangc and
Wenjie Tand
a Dep. of Soil Pollution Control, Chinese Research Academy of Environ. Sci., Dayangfang 8, Beijing 100012, P.R. China
b School of Chemical Eng. and the Environ., Beijing Institute of Technology, Beijing 100081, P.R. China
c College of Civil and Environmental Eng., Univ. of Science & Technology Beijing, Beijing 100083, P.R. China
d Institute of Water Sciences, Beijing Normal Univ., Xinjiekou Wai Street 19, Beijing 100875, P.R. China
* Corresponding author (ligulax{at}vip.sina.com).
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ABSTRACT
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Organo-mineral aggregates in various fractions including clay, silt, fine sand, and coarse sand were isolated from a Chernozem in northeast China by ultrasonic dispersion in water followed by sedimentation. The physicochemical properties of different fractions were determined and the organo-mineral aggregates were characterized jointly with Fourier-transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), x-ray diffraction (XRD), and cross-polarization (CP) with magic-angle spinning (MAS) 13C nuclear magnetic resonance (NMR) spectrometry. The XRD patterns showed that clay was dominated by quartz and calcite, while the mineral assemblage of silt was composed of quartz, calcite, plagioclase, and trace amounts of mica and chlorite. The results from FTIR spectra were consistent with those from XRD. The SEM images indicated that the particle surface became smoother with increasing particle size. The CP-MAS 13C NMR spectra showed that the contents of aromatic C in clay, silt, fine sand, and coarse sand were 25.6, 28.19, 17.22, and 26.32%, respectively. The adsorption and desorption behaviors of polycyclic aromatic hydrocarbons on four soil fractions were investigated using phenanthrene as a model substrate. The adsorption and desorption isotherms for all the fractions were well described by the modified Freundlich equation, and batch experiments demonstrated that the adsorption capacity increased with decreasing particle size. The desorption capacities of phenanthrene on clay and silt were larger than that of sand. The organic C normalized adsorption coefficients were positively correlated with the contents of nonpolar and aromatic C. The adsorption mechanism may be that phenanthrene undergoes a 
– interaction with organic matter of aggregates and is adsorbed on the aggregates.
Abbreviations: CEC, cation exchange capacity • CP, cross-polarization • FTIR, Fourier-transform infrared • MAS, magic-angle spinning • NMR, nuclear magnetic resonance • PAH, polycyclic aromatic hydrocarbon • SEM, scanning electron microscopy • SSA, specific surface area • XRD, x-ray diffraction
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INTRODUCTION
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Chemical reactions in soil mostly occur on the surface of soil organo-mineral aggregates, for example ion exchange and adsorption, ion diffusion, and the acid–base balancing. These reactions are directly or indirectly affected by the surface properties of soil organo-mineral aggregates. Organic matter can be closely associated with the mineral matter in soil. This association is one of the fundamental features that distinguish soils from their geological parent materials. Furthermore, organo-mineral particles, the main existing form of organic and mineral colloids in soils, are the main reservoirs of plant nutrients. Their surface properties, such as charge characteristics and complexation capacities, enable the retention of inorganic and organic pollutants. Hence organo-mineral aggregates are an important factor for pollutant transportation and retention. Most studies on naturally occurring organo-mineral aggregates have been concerned with the determination of C and N contents and how they are affected by agricultural treatment (Tiessen and Stewart, 1983; Christensen and Sorensen, 1986; Balesdent et al., 1988; Leinweber and Reuter, 1992). Investigations have also been performed on the adsorption of nutrients (Tiessen et al., 1983; Leinweber et al., 1997), heavy metals (Leinweber et al., 1995; Qian et al., 1996), and pesticides (Nkedi-Kizza et al., 1983; Huang et al., 1984) and polycyclic aromatic hydrocarbons (PAHs) (Hong et al., 2003; Jonker et al., 2005). Knowledge of the extent and mechanisms of PAH adsorption on naturally occurring organo-mineral aggregates of Chernozems, however, is still scarce.
Chernozems are the regional soils of Daqing, a city in the northeast of China, which has become an important oil industrial base. Polyaromatic hydrocarbons, produced mainly by incomplete combustion of fossil fuels, are known to be widespread contaminants in the natural environment, especially at oil-contaminated sites. Phenanthrene, a common PAH species in soil and sediment, is a main component of oil and has often been used in environmental research. It is known that phenanthrene and other PAHs show a great affinity to clay and organic matter in soils (Xing, 2001; Zhou et al., 2004). Thus, adsorption–desorption processes play an important role in PAH transportation and the degradation and remediation of contaminated soils.
We studied the characteristics of phenanthrene adsorption and desorption on different fractions of organo-mineral aggregates isolated from Chernozems in the northeast of China. A modified Freundlich model was fitted to phenanthrene adsorption and desorption, and the adsorption and resistance capacities of different soil fractions were compared, providing a theoretical basis for remediation.
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MATERIALS AND METHODS
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Soil Samples
The Chernozem soil samples were collected in Daqing, in Heilongjiang Province in the northeast of China. Four soil samples were collected in an area of 500 m2. Each soil sample consisted of a mixture of six subsamples from the top 20 cm of soil. The samples were dried at room temperature and stored for further analysis. They contained 10.23 g/kg organic matter and had a pH value of 7.52 in water suspension (1:1 [w/w] soil/water ratio).
Soil Organo-Mineral Aggregate Preparation
Naturally occurring organo-mineral aggregates were isolated by the following method (Edwards and Bremner, 1967). Fifty grams of each soil sample was put into a 250-mL flask and 50 mL of saturated NaCl solution was added. After the sample was ground into a paste with a glass stick with a rubber head, distilled water was added to the soil to a total volume of 150 mL. The suspended plant residues on the liquid surface of the NaCl solution were removed after thorough agitation and centrifugation, and this process was repeated three or four times until there was no plant debris on the liquid surface. The samples were then treated with ultrasonic vibration for 30 min. From the remaining suspension, clay (<2 µm), silt (2–20 µm), fine sand (20–200 µm), and coarse sand (>200 µm) fractions were separated by repeated sedimentation and syphoning off the suspension at the appropriate depths. The particle-size fractionation was repeated until a clear supernatant liquid was obtained. The fractions were dried at 45°C, ground, and stored.
Characterization of Organo-Mineral Aggregates
The pH was measured for a mixture of 1:1 (w/w) soil/water with a glass pH electrode. The organic matter content was measured by the colorimetric method using chromic acid, and the cation exchange capacity (CEC) was determined by following the procedure reported by Hendershot and Duquette (1986). Specific surface areas (SSAs) were measured by the N2 adsorption BET method using a NOVA 4200e surface area analyzer (Quantachrome Instruments, Boynton Beach, FL). Mineralogical analyses and characterization of organo-mineral aggregates were performed by x-ray diffractometry using a Rigaku Geigerflex D/Max-RC x-ray diffractometer with Cu K
radiation generated at 50 kV and 70 mA, at a scanning speed of 5° 2
/min (Rigaku, The Woodlands, TX). Organo-mineral aggregates isolated from the soil samples were characterized by their Fourier-transform infrared (FTIR) spectra. The spectra were recorded by FTIR spectrometer (Nicolet 5 PC, software Omnic 1.2 b, Thermo Fisher Scientific, Waltham, MA) using KBr pellets obtained by uniformly pressing a mixture of a 0.0015-g sample and 0.15 g of KBr. A scanning electron microscope (Hitachi S-450 with a Kevex energy dispersive system, Hitachi High Technologies, Schaumburg, IL) was used to obtain images of the different soil fractions. The dried sample powder was embedded in a polymer and coated with gold. The scanning electron microscope was operated at a 20 keV accelerating voltage under a vacuum chamber pressure of <13.33 mPa. The solid-state 13C nuclear magnetic resonance (NMR) spectra of organo-mineral aggregates were acquired using cross-polarization (CP) and magic angle spinning (MAS) techniques. The NMR spectrometer was a Bruker AM 300 spectrometer, equipped with a HP WP 73A probe (Bruker Optics, Bellerica, MA). The spectrometer was operated using the standard ramp CP pulse program. Approximately 300 mg of aggregate sample was packed into a 7-mm zirconium rotor with a kel-f cap. The acquisition parameters were a spectral frequency of 74.45 MHz, spinning rate of 4 kHz, ramp CP contact time of 1.5 ms, pulse width of 5.50 µs, and acquisition time of 70 ms.
Adsorption and Desorption of Phenanthrene on Soil Organo-Mineral Aggregates
Phenanthrene (95%) obtained from Aldrich Chemical Co. (Milwaukee, WI) was dissolved into methanol to prepare a concentrated stock solution (1 g/L). All the adsorption isotherms were obtained using a batch equilibration technique (Gunasekara et al., 2003) at 25°C in a 100-mL stoppered glass conical flask. The background solution was 0.01 mol/L CaCl2 in deionized, distilled water with 100 mg/L NaN3 as a biocide. Phenanthrene concentrations ranged from 0.05 to 1.0 mg/L. Due to the low water solubility (1.15 mg/L), phenanthrene was dissolved into methanol before being added to the background solution. Methanol concentrations were always <0.1% of the total solution volume to avoid cosolvent effects (Rao et al., 1985). An exact amount of 50 mg of organo-mineral aggregate was weighed into the flask. Different concentrations of 50 mL aqueous solution of phenanthrene were added to each flask with the organo-mineral aggregates. Each isotherm curve consisted of seven concentration points, and each point, including the blank, was run in triplicate. The flasks with organo-mineral aggregates and an aqueous solution of phenanthrene were then shaken (150 rpm) for 50 h at 25°C for equilibration. The flasks were then centrifuged at 3000 rpm for 20 min, and the supernatant was removed for the estimation of phenanthrene. For desorption, batch equilibration was performed by replacing the supernatant with 0.01 mol/L CaCl2 solution. The remaining slurry in the flasks was refilled to the original volume by adding 50 mL of 0.01 mol/L CaCl2 solution and re-equilibrating for 50 h. All the experiments were performed in triplicate.
Concentrations of phenanthrene in the supernatant were analyzed using a fluorescence spectrometer (F-4010, Hitachi, Tokyo). The emission wavelength was 346 nm and the excitation wavelength was 250 nm. Because there was little adsorption by the flasks and no biodegradation, phenanthrene sorbed by the sorbents was calculated by the mass difference:
where q is the specific adsorbed amount of solute (g/kg), V is the volume of the equilibrium solution (L), Ci is the initial and C is the equilibrium concentration of phenanthrene (mg/L), and m represents the weighed amount of organo-mineral aggregates (g).
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RESULTS AND DISCUSSION
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Characterization of Soil Organo-Mineral Aggregates
The selected properties of four particle-sized organo-mineral aggregates are listed in Table 1
. The coarse sand fraction of the Chernozem tended to be larger than the finer fractions. The clay fraction showed the highest organic matter content, the largest SSA, and the greatest CEC. The CEC decreased with increasing particle size of the fractions. The coarse sand fraction had the lowest CEC (1.50 cmol/kg), equivalent to 1/30 of the CEC level of the clay fraction, which is perhaps attributable to the size of the structural channel and cavities that apparently block some exchange ions. The N2 SSA also increased with decreasing particle size.
Different particle-sized organo-mineral aggregates were characterized by x-ray diffraction (XRD) and interpreted (Fig. 1
). The sharp and prominent peaks at 3.348, 2.46, 2.283, 2.129, and 0.1819 nm suggest the presence of quartz in all fractions (Kumar et al., 2001). A strong peak at 0.3038 nm indicates the existence of calcite in the clay and silt fractions (Carroll, 1970; Kumar et al., 2001). The presence of feldspar is confirmed by peaks at 0.4041, 0.3776, and 0.3195 nm in the silt fraction (Kumar et al., 2001). A trace amount of chlorite is identified at 0.711 nm. The 0.449-nm peak indicates the presence of mica (Kumar et al., 2001). X-ray diffraction patterns show that clays were dominated by quartz and calcite, while the mineral content of silt consisted of quartz, calcite, plagioclase, and trace amounts of mica and chlorite. Thus, except for some differences in the amounts of mineral components, all the fractions had relatively similar mineralogical compositions.
The scanning electron microscopy (SEM) images (Fig. 2
) clearly indicate the difference in particle sizes of the soil fractions. It was found that the particle surface had a smoother appearance with increasing particle size. The SEM of the clay fraction (Fig. 2A) revealed numerous small discrete particles scattered among the microaggregates. The silt fraction (Fig. 2B) had some small particle-like soil microaggregates and some larger particles with a relatively smooth appearance. The surface of silt was rougher, however, than the fine sand. The smooth surface of the particles in the coarse sand fraction (Fig. 2D) suggests they were crystalline. Indeed, most must have been quartz, as quartz was the most abundant mineral phase in this fraction from the above XRD results. Meanwhile, the surface of coarse sand particles was smooth, indicating that these particles were either uncoated or had a very thin coating of organic matter.
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Fig. 2. Scanning electron micrographs of different fractions of organo-mineral aggregates: (A) clay; (B) silt; (C) fine sand; (D) coarse sand.
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The infrared spectra of organo-mineral aggregates of the Chernozem are shown in Fig. 3
. In general, the spectra of all four fractions were very similar and show the same prominent bands at 3427, 1639, 1460, 1040, 879, and 778 cm–1, which suggest aggregates due to the presence of montmorillonite (Gan and Zhang, 1992; Song et al., 1994). The broad intense band at approximately 3427 cm–1 was due to the stretching vibration of bound and unbound hydroxyl groups (Piccolo et al., 1992). The broad band at about 1639 cm–1 is assigned to C=O vibrations of carboxylates and aromatic vibrations (Piccolo et al., 1992). The bands at 1460 and 879 cm–1 are the characteristic peaks of calcite (Gan and Zhang, 1992). The band at 1040 cm–1 is assigned to Si–O vibrations of clay minerals. Bands at 692 and 526 cm–1 were also due to inorganic materials, such as clay and quartz minerals (Gan and Zhang, 1992). The two adsorption bands at 778 and 797 cm–1 are attributed to silica of weathered quartz, of which the band at 797 cm–1 indicates the presence of undefined silica (Gan and Zhang, 1992). In infrared spectra of the four fractions, the characteristic band of quartz is mainly at 778 cm–1, which indicates the weakly weathered crystal structure of quartz. Furthermore, with increasing particle size, the relative absorbances increased, which suggests that the amount of quartz became larger. The slight decline of the relative absorbance of the bands at 1460 and 879 cm–1 with increasing particle size demonstrates that the content of calcite in the corresponding fraction decreased. The two results coincide with those of the XRD analysis.
Figure 4
is the CP-MAS 13C NMR spectra of the four organo-mineral aggregates isolated from the Chernozem. Within the chemical shift range of 0 to 220 ppm, the NMR spectra are divided into five regions (Xing, 2001; Maie et al., 2002): C atoms at 0 to 50 ppm are assigned to alkyl C, 50 to 110 ppm to O-alkyl C, 110 to 165 ppm to aromatic C, 165 to 190 ppm to carboxyl C, and 190 to 220 ppm to carbonyl C. The NMR integration results are listed in Table 2
. The strong resonance around 170 ppm is attributed to carboxyl C and that at 130 ppm represents aromatic C (Salloum et al., 2002). Among the structural C, O-alkyl C, carboxyl C, and carbonyl C are polar and have a greater affinity for hydrophilic compounds. A polar C contributes to the adsorption of polar contaminants (De Paolis and Kukkonen, 1997). Alkyl C and aromatic C are nonpolar and contribute to the adsorption of nonpolar organic pollutants. The contents of nonpolar C (alkyl C + aromatic C) in clay, silt, fine sand, and coarse sand were 54.33, 52.74, 47.37, and 52.19%, respectively (Table 2). At the same time, the content of aromatic C in the silt fraction was the largest. All these results may affect the adsorption capacity and modeling of the four types of aggregates for phenanthrene.
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Fig. 4. Solid-state cross-polarization magic angle spinning 13C nuclear magnetic resonance spectra of organo-mineral aggregates: (a) clay; (b) silt; (c) fine sand; (d) coarse sand.
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Adsorption and Desorption Isotherms
Adsorption of organic pollutants by heterogeneous sorbents such as soils and soil components is often described by the Freundlich equation, which is written as
where q and Ce are the solid-phase and liquid-phase equilibrium concentrations (g/kg and mg/L), respectively; Kf is the Freundlich affinity coefficient, and n is the Freundlich exponential coefficient. The Kf has different dimensions for different values of n, however, so we used the modified Freundlich equation (Carmo et al., 2000), which is written as
where Cr is the relative equilibrium concentrations of the sorbate (Cr = Ce/Sw, where Sw is the solubility of the sorbent in water), which is dimensionless; KF is the modified Freundlich affinity coefficient, and although n is different, the unit of KF is the same as that of q. Hence values of KF can be compared directly to evaluate the adsorption capacity.
Freundlich isotherm parameters are presented in Tables 3
and 4
and isotherms of phenanthrene for the four fractions are shown in Fig. 5
. The data in Tables 3 and 4 show that both adsorption and desorption procedures of the four fractions were nonlinear with different extents. Moreover, clay exhibited a higher adsorption capacity than other fractions and KF values for the adsorption procedure increased with a decrease in particle size. For this phenomenon, Nkedi-Kizza et al. (1983) considered that it was the higher organic C content in finer particles that increased the adsorption capacity, whereas Weber et al. (1992) contributed it to the heterogeneity of properties of the sorbents. Many researchers also reported that the organic matter content in the sorbent was a major factor in controlling hydrophobic organic compound adsorption to soils and sediments (Chiou et al., 1998; Carmo et al., 2000; Weber et al., 2001). Hence, the increase in adsorption capacity with decreasing particle size is perhaps due to the larger organic matter content of finer particles. The linear fitting results between values and the properties of aggregates are listed in Table 5
. It was found that the KF value was positively correlated with the organic matter content, CEC, and SSA, although the SSA correlation was slightly lower. It suggests that organic matter content is an important factor in phenanthrene adsorption on organo-mineral aggregates. Many other studies of hydrophobic organic compound adsorption by soils and soil components have shown a similar correlation (Kile et al., 1995). Chernozems, which have an abundance of montmorillonite and contain more exchangeable Ca and Mg, can bind with humic acid of organic matter and affect the binding between phenanthrene and organic matter. The fact that the KF value is correlated with SSA indicates that the mineral compositions contribute to the adsorption of phenanthrene to a certain extent. In fact, the aggregates were formed by organic and mineral compositions, so both components were involved in the adsorption procedure. The result is consistent with studies on the adsorption of mineral materials (Hundal et al., 2001; Michael et al., 2002).
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Fig. 5. Adsorption and desorption isotherms of phenanthrene on different fractions: (A) adsorption; (B) desorption. Cr is the relative equilibrium concentration of the sorbate and q is the solid-phase equilibrium concentration.
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Furthermore, the adsorption nonlinearity varied from 0.896 to 0.9646. The clay fraction exhibited the most nonlinearity, with an n value of 0.896, while fine and coarse sand had n values of 0.9623 and 0.9646, respectively. Therefore the adsorption mechanism might be different for these fractions. Pignatello and Xing (1996) and Xing et al. (1996) proposed the dual-mode adsorption model in which there exists both a partition domain and a hole-filling domain in natural sorbents, with the adsorption possibly involved in both domains. From the above results, it is known that the clay fraction had the largest SSA, the roughest surface, and the highest adsorption capacity. It can thus be speculated that the clay fraction was more able to adsorb humic substances and perhaps contained a greater adsorption domain such as condensed organic matter, as described by Weber and Huang (1996). The fine and coarse sand perhaps contained a greater partition domain, thus having higher n values.
The organic C normalized adsorption coefficients (Koc) are calculated by dividing KF values by the respective fraction of organic C (foc) in the samples. The values of Koc are also listed in Table 3. The correlations between phenanthrene Koc values and the contents of nonpolar C, aromatic C, and alkyl C are listed in Table 6
. The correlation between Koc values and nonpolar C is good, which is consistent with previous conclusions. Furthermore, Koc values correlate well with the aromatic C contents, while Koc values have a poor correlation with the alkyl C contents. This is consistent with previous results (Xing et al., 1994). The above implies that the aromatic C content of aggregates may dominate the adsorption capacity of phenanthrene on the aggregates. The interaction between aggregates and phenanthrene is performed by the aromatic C of the aggregates. Some researchers have proposed that the sorption mechanism of PAHs on soils is the overlap of electrons in the aromatic soot structure and the planar aromatic ring of PAH molecules (Hawthorne et al., 2002; Hong et al., 2003). Another study considered that the phenanthrene molecules' adsorption mechanism on humic acids was first adsorption into the inner three-dimensional structure of humic acids and then the formation of the – conjugation system (Xu et al., 2005). Therefore in this study, phenanthrene may undergo a – interaction with the organic matter of aggregates and be adsorbed on the aggregates.
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Table 6. Correlation between adsorption organic C normalized adsorption coefficient values and content of structural C.
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Comparing the KF and n values in Tables 3 and 4, it is found that the values of the adsorption isotherms for phenanthrene were lower than those of their respective desorption curves, indicating apparent hysteresis possibly due to irreversible fixation such as surface complexation and especially rate-limiting intra- and interparticle diffusion processes (Wang et al., 1993; Altfelder et al., 2000), which is consistent with reported results (Bhandari et al., 1997; Huang and Weber, 1997). Huang and Weber (1997) defined the hysteresis index (HI) as
whereqeD and qeSare the concentrations of sorbate during adsorption and desorption, respectively. The HIs in different relative equilibrium concentrations of 0.01, 0.1, and 0.2 were calculated and are listed in Table 4. It can be seen that under each relative equilibrium concentration, the HI values decreased with increasing particle size. From Fig. 5B, it can be seen that the desorption capacities of clay and silt were higher than those of fine and coarse sand. It has been demonstrated that phenanthrene interacted simultaneously with both organic and mineral portions when adsorbed on the soil organo-mineral aggregates. The strength of adsorption to soil minerals was weaker than that to organic matter, resulting in a smaller increase of distribution coefficients at the desorption step. Thus, phenanthrene bound on organic matter was difficult to desorb, while that on minerals was easy to dissolve again in the aqueous phase.
Figure 6
shows the adsorption and remaining amount (the difference between adsorption and desorption amounts at equilibrium concentration) of phenanthrene on the four fractions and their relationship with organic matter content. The adsorption and remaining amount of phenanthrene in different fractions of organo-mineral aggregates in the Chernozem increased with the increasing organic matter content. The adsorption and resistance capacity are largely dependent on organic matter content, and the clay fraction had a relatively high capacity for adsorption and resistance to desorption. The structural characteristics and adsorption behavior of the different fractions of the Chernozem organo-mineral aggregates will help in understanding their environmental behavior with organic contaminants.
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Fig. 6. Adsorption and remaining capacity of phenanthrene on different fractions. q is the solid-phase equilibrium concentration.
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CONCLUSIONS
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The clay fraction of the tested Chernozem showed the highest organic matter content, the largest surface area, and the greatest cation exchange capacity among the four fractions of soil aggregates. All the fractions had similar mineralogical compositions, dominated by quartz and calcite, but some differences existed in the amount of the mineral components. The SEM images of the soil fractions indicated that the particle surface became smoother with increasing particle size. The adsorption and desorption isotherms in all fractions were well described by the modified Freundlich equation, and batch experiments demonstrated that the adsorption capacity increased with decreasing particle size. It is also evident that desorption of phenanthrene presented apparent hysteresis. The desorption capacities of clay and silt were larger than that of sand. It was demonstrated that phenanthrene interacted simultaneously with both organic and mineral portions when adsorbed on the soil organo-mineral aggregates. The adsorption and resistance capacity is largely dependent on organic matter content, and the clay fraction had high capacities of adsorption and desorption. The Koc value is positively correlated with the content of nonpolar and aromatic C. The adsorption mechanism may be that phenanthrene undergoes a – interaction with organic matter of aggregates and is adsorbed on the aggregates.
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ACKNOWLEDGMENTS
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We greatly appreciate the Natural Science Foundation of China (no. 20677055), China National Basic Research Program (no. 2004CB418501), and National Scientific and Technological Platform Program (2004DEA70890) for the funding of this research. We are also grateful to Prof. F. Zhang, Institute of Soil & Fertilizer, Chinese Academy of Agricultural Sciences, for his assistance in obtaining soil samples, and Dr. S. Zhao, Department of Environmental Analysis, China National Environmental Monitoring Center, for her valuable comments and suggestions.
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NOTES
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All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication November 17, 2006.
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REFERENCES
|
|---|
- Altfelder, S., T. Streck, and J. Richter. 2000. Nonsingular sorption of organic compounds in soil: The role of slow kinetics. J. Environ. Qual. 29:917–925.[Abstract/Free Full Text]
- Balesdent, J., G.H. Wagner, and A. Mariotti. 1988. Soil organic matter turnover in long-term field experiments as revealed by carbon-13 natural abundance. Soil Sci. Soc. Am. J. 52:118–124.[Abstract/Free Full Text]
- Bhandari, A., J.T. Novak, W.D. Burgos, and D.F. Berry. 1997. Irreversible binding of chlorophenols to soil and its impact on bioavailability. J. Environ. Eng. 123:506–512.[CrossRef]
- Carmo, A.M., L.S. Hundal, and M.L. Thompson. 2000. Sorption of hydrophobic organic compounds by soil materials: Application of unit equivalent Freundlich coefficients. Environ. Sci. Technol. 34:4363–4369.
- Carroll, D. 1970. Clay minerals: A guide to their x-ray identification. Geol. Soc. Am., Boulder, CO.
- Chiou, C.T., S.E. McGroddy, and D.E. Kile. 1998. Partition characteristics of polycyclic aromatic hydrocarbons on soils and sediments. Environ. Sci. Technol. 32:264–274.
- Christensen, B.T., and L.H. Sorensen. 1986. Nitrogen in particle size fractions of soils incubated for five years with 15N-ammonium and 14C-hemicellulose. J. Soil Sci. 37:241–247.[CrossRef]
- De Paolis, F., and J. Kukkonen. 1997. Binding of organic pollutants to humic and fulvic acids: Influence of pH and the structure of humic material. Chemosphere 34:1693–1704.
- Edwards, A.P., and J.M. Bremner. 1967. Dispersion of soil particles by sonic vibration. J. Soil Sci. 18:47–63.[CrossRef]
- Gan, H.M., and Y.P. Zhang. 1992. Preliminary study on the characteristics of infrared spectrum of five soils in Shaanxi. (In Chinese.) Acta Pedol. Sin. 29(2):232–236.
- Gunasekara, A., M.J. Simpson, and B. Xing. 2003. Identification and characterization of sorption domains in soil organic matter using structurally modified humic acids. Environ. Sci. Technol. 37:852–858.[Medline]
- Hawthorne, S.B., D.G. Poppendieck, C.B. Grabanski, and R.C. Loehr. 2002. Comparing PAH availability from manufactured gas plant soils and sediments with chemical and biological tests: 1. PAH release during water desorption and supercritical carbon dioxide extraction. Environ. Sci. Technol. 36:4795–4803.[Medline]
- Hendershot, W.H., and M. Duquette. 1986. A simple barium chloride method for determining cation capacity and exchangeable cations. Soil Sci. Soc. Am. J. 50:605–608.[Abstract/Free Full Text]
- Hong, L., U. Ghosh, T. Mahajan, R.N. Zare, and R.G. Luthy. 2003. PAH sorption mechanism and partitioning behavior in lampblack-impacted soils from former oil–gas plant sites. Environ. Sci. Technol. 37:3625–3634.[Medline]
- Huang, P.M., R. Grover, and R.B. McKercher. 1984. Components and particle-size fractions involved in atrazine adsorption by soils. Soil Sci. 138:20–24.
- Huang, W., and W.J. Weber, Jr. 1997. A distributed reactivity model for sorption by soils and sediments: 10. Relationships between desorption, hysteresis and the chemical characteristics of organic domains. Environ. Sci. Technol. 31:2562–2569.
- Hundal, L.S., M.L. Thompson, D.A. Laird, and M. Carmo. 2001. Sorption of phenanthrene by reference smectites. Environ. Sci. Technol. 35:3456–3461.[Medline]
- Jonker, M.T.O., S.B. Hawthorne, and A.A. Koelmans. 2005. Extremely slowly desorbing polycyclic aromatic hydrocarbons from soot and soot-like materials: Evidence by supercritical fluid extraction. Environ. Sci. Technol. 39:7889–7895.[Medline]
- Kile, D.E., C.T. Chiou, H. Zhou, H. Li, and O. Xu. 1995. Partition of non-polar organic pollutants from water to soil and sediment organic matters. Environ. Sci. Technol. 29:1401–1410.
- Kumar, M., S.K. Ghosh, and K.M. Manjaiah. 2001. Mineralogical composition of the organo-mineral complexes from some soils of Himachal Pradesh. J. Nucl. Agric. Biol. 30(1):12–24.
- Leinweber, P., L. Haumaier, and W. Zech. 1997. Sequential extractions and 31P-NMR spectrometry of phosphorus forms in animal manures, whole soils and particle-size separates from a densely populated livestock area in northwest Germany. Biol. Fertil. Soils 25:89–94.[CrossRef]
- Leinweber, P., C. Paetsch, and H.-R. Schulten. 1995. Heavy metal retention by organo-mineral particle-size fractions from soils in long-term agricultural experiments. Arch. Acker-Pflanzenbau Bodenkd. 39:271–285.
- Leinweber, P., and G. Reuter. 1992. The influence of different fertilization practices on concentrations of organic carbon and total nitrogen in particle-size fractions during 34 years of a soil formation experiment in loamy marl. Biol. Fertil. Soils 13:119–124.[CrossRef]
- Maie, N., A. Watanabe, K. Hayamizu, and M. Kimura. 2002. Comparison of chemical characteristics of Type A humic acids extracted from subsoils of paddy fields and surface soils. Geoderma 106:1–19.[CrossRef][Web of Science]
- Michael, J.A., B.F. Milena, and J. Ikhsan. 2002. The sorption of anthracene onto goethite and kaolinite in the presence of some benzene carboxylic acids. J. Colloid Interface Sci. 247:282–289.[CrossRef][Web of Science][Medline]
- Nkedi-Kizza, P.S., P.S.C. Rao, and J.W. Johnson. 1983. Adsorption of diuron and 2,4,5-T on particle-size separates. J. Environ. Qual. 2:195–197.
- Piccolo, A., P. Zaccheo, and P.G. Genevini. 1992. Chemical characterization of humic substances extracted from organic-waste-amended soils. Bioresour. Technol. 40:275–282.[CrossRef][Web of Science]
- Pignatello, J.J., and B. Xing. 1996. Mechanisms of slow sorption of organic chemicals to natural particles. Environ. Sci. Technol. 30:1–11.
- Qian, J., X. Shan, Z. Wang, and Q. Tu. 1996. Distribution and plant availability of heavy metals in different particle-size fractions of soil. Sci. Total Environ. 187:131–141.[CrossRef]
- Rao, P.S.C., A.G. Hornsby, D.P. Kilcrease, and P. Nkedi-Kizza. 1985. Sorption and transport of hydrophobic organic chemicals in aqueous and mixed solvent systems: Model development and preliminary evaluation. J. Environ. Qual. 14:376–383.[Abstract/Free Full Text]
- Salloum, M.J., B. Chefetz, and P.G. Hatcher. 2002. Phenanthrene sorption by aliphatic-rich natural organic matter. Environ. Sci. Technol. 36:1953–1958.
- Song, X.M., S.X. Lu, Z.G. Xu, C.L. Li, and F.Y. Liu. 1994. Structural characterization of nickel-substituted mica montmorillonite. (In Chinese.) J. East China Univ. Sci. Technol. 20(4):528–534.
- Tiessen, H., and J.W.B. Stewart. 1983. Particle size fractions and their use in studies of soil organic matter: II. Cultivation effects on organic matter composition in size fractions. Soil Sci. Soc. Am. J. 47:509–514.[Abstract/Free Full Text]
- Tiessen, H., J.W.B. Stewart, and J.O. Moir. 1983. Changes in organic and inorganic phosphorus composition of two grassland soils and their particle size fractions during 60–90 years of cultivation. J. Soil Sci. 34:815–823.
- Wang, L., R., Govind, and R.A. Dobbs. 1993. Sorption of toxic organic compounds on wastewater solids: Mechanism and modeling. Environ. Sci. Technol. 27:152–158.
- Weber, W.J., Jr., and W.L. Huang. 1996. A distributed reactivity model for sorption by soils and sediments: 4. Intraparticle heterogeneity and phase-distribution relationships under nonequilibrium conditions. Environ. Sci. Technol. 30:881–888.
- Weber, W.J., Jr., E.J. Leboeuf, T.M. Young, and W.L. Huang. 2001. Contaminant interactions with geosorbent organic matter: Insights drawn from polymer sciences. Water Res. 35:853–868.[Medline]
- Weber, W.J., Jr., P.M. McGinley, and E.K. Lynn. 1992. A distributed reactivity model for sorption by soils and sediments: 1. Conceptual basis and equilibrium assessments. Environ. Sci. Technol. 26:1955–1962.
- Xing, B. 2001. Sorption of naphthalene and phenanthrene by soil humic acids. Environ. Pollut. 111:303–309.[CrossRef]
- Xing, B., W.B. McGill, and M.J. Dudas. 1994. Cross-correlation of polarity curves to predict partition coefficients of nonionic organic contaminants. Environ. Sci. Technol. 28:1929–1933.
- Xing, B., J.J. Pignatello, and B. Gigliotti. 1996. Competitive sorption between atrazine and other organic compounds in soils and model sorbents. Environ. Sci. Technol. 30:2432–2440.
- Xu, D.P., S.Q. Zhu, H. Chen, and F.S. Li. 2005. Structural characterization of humic acids isolated from typical soils in China and their adsorption characteristics to phenanthrene. Colloids Surf. A 276:1–7.[CrossRef]
- Zhou, Y.M., R.X. Liu, and H.X. Tang. 2004. Sorption interaction of phenanthrene with soil and sediment of different particle sizes and in various CaCl2 solutions. J. Colloid Interface Sci. 270:37–46.[CrossRef][Web of Science][Medline]
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ABSTRACT
INTRODUCTION
